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Jumper (yellow) for overclocking a Celeron processor

As overclocking ( English overclocking ) is the operation of processors , or other computer components ( hardware components) having a higher clock frequency above the normal manufacturer specification referred to, with the aim of a higher computing power to achieve. The opposite of this is underclocking , which is mostly used as an energy saving measure or with the aim of a longer service life .

Occasionally, functions for dynamically increasing the processor clock are also referred to as overclocking , such as AMD's Turbo Core Technology and Intel's Turbo Boost Technology . However, this is a clock increase intended by the manufacturers within a specified range.


Increasing the clock rates of components such as B. CPU , graphics card or memory , results in an increase in the performance of the overall system.

This is made possible because the manufacturers design only a few versions of a microchip due to the development and production costs. Furthermore, the quality of the microchips produced on a wafer differ in that the heat development varies at the same clock rate.


Small microchips are overclocked by replacing the clock generator (a quartz crystal ).

In order to keep the system stable even at higher clock rates, the operating voltage (in CPUs, the core voltage ) is often increased. However, this can lead to overheating and other problems (see section Hazards ).

The clock rate of a component of a computer can usually be set in the BIOS and / or by special software during operation. Older mainboards also often have jumpers for frequency setting . With CPUs, the clock is made up of a reference clock and a multiplier . For example, a reference clock of 200 MHz and a multiplier of 10 results in a processor clock of 2000 MHz. The reference clock is classically the clock of the Front Side Bus (FSB); Since modern CPUs no longer have an FSB, a different clock, for example the Uncore clock , is used today. In many cases, an increase in the reference clock also increases the clock of components other than the CPU (e.g. buses or the memory). The multiplier is locked on many CPUs so that they can only be overclocked using the reference clock.


Overclocked systems can become unstable and produce (arithmetic) errors. These express themselves in a system crash, crashing programs or similar undesirable properties. When overclocking a PC system, the process is usually gradual. Stability tests are carried out after every clock increase. The stability after overclocking is often tested with programs that fully utilize the component, such as Prime95 for processors. If the overclocked system survives the so-called torture test , which lasts several hours , it is usually regarded as stable.


If components are operated outside of their specifications, the manufacturer's guarantee is void in almost all cases . The life expectancy of overclocked components can also decrease significantly.

Electromigration is favored by a higher clock rate and, above all, the increased voltage . B. became known as Sudden Northwood Death Syndrome . The power loss increases linearly with the cycle and quadratically with the voltage.

Another source of danger is the heat generated when overclocking. While overclocking too much, too little cooling or cooling failures led to overheating damage in older CPU models, there is now a technique called throttling that prevents the processor from getting too hot by simply skipping clocks. However, doing so can result in lower performance, making overclocking counterproductive.


Due to the increased power loss, improved cooling is usually necessary for overclocking. In the case of processors, this can be achieved through good air coolers, water cooling , compressor cooling , dry ice and liquid nitrogen . However, dry ice and nitrogen are primarily used to achieve overclocking records.

Record hunt

Some overclockers work for profit, mostly for relevant websites that are sponsored by advertising. The goal is to overclock CPUs as high as possible. There are different categories, both in terms of cooling (e.g. no restriction, water cooling, air cooling) and the necessary stability (e.g. BIOS bootable, Windows bootable (usually until the GUI appears ), prime-stable ). A distinction is also made between CPU manufacturer, processor type and chipset. In addition, there are record attempts that are not about the highest possible clock rate, but about the best performance in certain benchmarks, e.g. B. 3DMark , Super PI or SiSoft Sandra .


In 2013 an Intel Celeron 347 was overclocked from 3,066 MHz to over 8,398.07 MHz. That was the world record for Intel processors at the time.

Shortly before the official presentation of the Bulldozer series, AMD presented a record, an AMD Bulldozer-FX was overclocked to 8,429.4 MHz. It was cooled with liquid helium.

Web links

Commons : Overclocking  - collection of pictures, videos and audio files

Results databases

Individual evidence

  1. Chong-Min Kyung, Sungjoo Yoo (Ed.): Energy-Aware System Design . Springer, Netherlands 2011, ISBN 978-94-007-9258-6 , pp. 12 ( limited preview in Google Book search).
  2. https://www.informit.com/articles/article.aspx?p=130978&seqNum=12
  3. World record set in overclocking with Intel Celeron http://www.pcgameshardware.de/CPU-Hardware-154106/News/Celeron-347-OC-Weltrekord-1044060/
  4. http://www.pcgameshardware.de/CPU-Hardware-154106/News/Overclocking-Weltrekord-mit-Bulldozer-FX-8429-MHz-von-AMD-erreich-Update-844385/